1. Field of the Invention
The present invention concerns a path establishing method in a wireless network environment and a wireless network device therefor. Particularly, the present invention concerns a wireless network device for establishing an optimal path by calculating and using information on a redundant path and recovering a lost path by using the redundant path and a method thereof.
2. Description of the Related Art
Development of Internet and wireless communication technologies has contributed to delivery of diverse multimedia services beyond time and location, to thus give rise to significant changes to life environment of users. Recently, as compact handheld electronic devices, such as a notebook computer and a personal digital assistant (PDA), have come into wide use, more efforts are made toward implementation of Internet-based data communication in a wireless network as well as in a wired network.
A representative of the wireless network is an ad-hoc network. The ad-hoc network has no integrated central management device, does not use existing communication infrastructure, and has no fixed controller (such as a router, a host, and a radio base station) for connecting mobile nodes. A mobile node serves as a router in the ad-hoc network. If a certain mobile node intends to communicate with a correspondent node, the certain node needs to establish a communication path via several nodes located between the certain node and the correspondent node.
For example, such an ad-hoc network may be a sensor network including a plurality of sensors. Progress of wireless communication enables development of a sensor node with low cost, low power, and multifunction. Operations such as sensing, data processing, and communicating, can be performed by implementing a sensor network including such compact sensor nodes. The sensor network includes a plurality of the sensor nodes, densely distributed. Implementation of a routing protocol is required among the sensor nodes having only an air interface to collect and deliver required information using the sensor nodes. It is required to suitably deal with situations due to free movement of the sensor nodes.
FIG. 1 illustrates a path establishment in a conventional wireless network including the plurality of the mobile nodes. Referring to FIG. 1, when a source node N1 of the mobile nodes intends to transfer information to a destination node N11, the information may be transferred via the other nodes located between the source node N1 and the destination node N11 when it is impossible to deliver the information directly from the source node N1 to the destination node N11. That is, the information may be transferred along a path established via the other nodes. The path is established by switching a route request (RREQ) packet and a route reply (RREP) packet. Concretely, if the source node N1 transmits a RREQ packet to adjacent nodes N2 and N3, the nodes N2 and N3 register the source node N1, which transmits the RREQ packet as an upstream node, and transmits the received RREQ packet to adjacent nodes N4 and N6. The RREQ packet contains an ID of the destination node N11. Each intermediate node receiving RREQ packets determines whether the receiving node is the destination node N11. If the receiving node is not the destination node, the intermediate node forwards the RREQ packet to a next hop node, or if the receiving node is the destination node, the intermediate node selects an optimal path by checking information on the intermediate nodes contained in the received RREQ packet and forwards a RREQ packet in an inverse direction of the RREQ packet transmission. In the conventional arrangement, a shortest path, namely a path having a smallest number of the intermediate nodes is selected as the optimal path for the swift information delivery. That is, the destination node N11 transmits the RREP packet toward an upstream router transmitting the RREQ packet via the smallest number of the intermediate nodes. When the source node N1 receives the RREP packet, the path is established between the source node N1 and the destination node N11.
However, the conventional arrangement has a disadvantage that quality of service (QoS) is not provided selectively depending on characteristics of data to be transferred. The selected optimal path is advantageous for the swift information delivery, but is not suitable for data requiring stable delivery rather than the swift delivery.
Referring again to FIG. 1, if the node N4 has a failure, or, if the established path is lost due to the node movement to other directions, a new path has to be established between the source node N1 and the destination node N11, thus requiring more time for path recovery and node rediscovery.